1. Field of the Invention
The present invention relates to a multi-cylinder engine for a vehicle, in which a pair of cylinder bore rows, each including a plurality of cylinder bores disposed in parallel to each other, are disposed in such a manner as to be perpendicular to a crank shaft disposed substantially in the horizontal direction.
2. Description of Related Art
A multi-cylinder engine of this type has been known, for example, from Japanese Patent Laid-open No. Sho 61-291760. This prior art multi-cylinder engine includes a pair of cylinder bore rows disposed in an approximately V-shape. The pair of cylinder bore rows is generally configured such that a single cam shaft is disposed on an extension of the axial lines of cylinder bores or a pair of cam shafts are disposed on both of the sides of the extension of the axial lines of the cylinder bores. Such a disposition of the cam shaft; however, causes a problem in that the valve system mechanisms containing the cam shafts are disposed in spaces on both sides of the extension of the axial lines of the cylinder bores.
On the other hand, in the case where a V-shaped multi-cylinder engine or a horizontally-opposed type multi-cylinder engine is mounted on a motorcycle in such a manner that the axial line of tile crank shaft extends in the longitudinal direction, it is required to ensure a relatively large space under a cylinder head for increasing the bank angle of the motorcycle and for ensuring a space allowing the driver's feet to extend forwardly under the cylinder head. However, the prior art disposition of the cam shaft fails to obtain a multi-cylinder engine capable of satisfying the above requirement.